1. Field of the Invention
The invention relates generally to a non-vapor system for detection of concealed contraband including: all types of explosives or drugs in carry-on baggages and hand-held items; contraband in checked-in baggage and air cargo as well as freight containers; explosives carded by individuals across a security check point, drugs concealed in hidden compartments aboard planes, leisure boats, or ships; and buried explosive-filled ordnance such as antipersonnel, anticraft, and antivehicle mines.
2. Background of the Invention
Shadowgraphs based upon radiographic imaging are currently in use for detection of explosives in carry-on baggage and articles in airports and at some security points at the entrance of secured buildings. Existing radiographic imaging provides low contrast images which are inadequate specially in identification of state-of-the-art explosives, weapons, and drugs. Plastic and water-based explosives may escape present interrogation capabilities. Reliance on humans in interpretation of radiographic displays is subject to the influence of a basic human trait which is temporal variability in response to stimuli. Such human factors may be compensated for when baggage interrogation results in high ram of false alarms. However, misses can defeat the whole objective of screening. As an interrogation device, shadowgraphs and line scanners are only useful as a deterrence to casual threats. This is aside from the fact that it is by far the least expensive and the most informative device in the market.
Due to the inadequacy of shadowgraph interpretation, airlines have instituted, in some international airports, their own search team as a second level of defense although radiographic screening, frisking, and visual screening are employed extensively in such airports. The process is usually a cause of delay and annoyance to passengers. Also, training security operators on handling explosives can be costly and would require special skills. Furthermore, the possibility of misses due to difficulty in visual recognition of a threat will remain a source of concern. Although airport baggage interrogation can be accomplished in principle, by automated conveyers and microprocessors, human involvement provides an additional level of deterrence.
Premeditated actions and advanced explosives technology and camouflage can possibly defeat existing screening arrangements. Also, screening stations are vulnerable to sabotage and can be a target for terrorist actions since suspected baggages are screened in the same spot as baggages containing benign objects. Apprehension of terrorists around the screening station and the procedure of inspection can expose innocent passengers to high risk. Generally, manual search of suspicious carry-on baggage or personal articles at security checking points involves an element of risk to operators, innocent individuals, passengers, or passers-by since accidental or inadvertent engagement of an explosive charge cannot be dismissed.
At security check points at airports or critical installations, screening of individuals for concealed explosives and contraband, using metal detectors, goes hand in hand with screening carry-on baggage. Existing metal detectors are not adequate for advanced plastic explosives and the potential spread of plastic guns. X-rays cannot be used on people due to the danger of ionizing radiation. Regardless of the level of exposure, the produced effects are undesirable. The use of sniffers employed in many security systems are likely to have low detection probability for military explosives and new water gel explosives, and hermetically sealed objects can defeat the whole detection system. A non-breachable security point will ultimately involve a system combining at least two techniques including sniffers (gas chromatography), metal detection, acoustics, etc. The redundancy provides a high confidence of establishing a hard-to-breach barrier against terrorists and illegal traffic of explosive and contraband.
Accordingly, there is a need in the art for: a cost-effective, integrated system for screening carry-on baggages and individuals at security check points which are not limited to vapor detection, which overcome the limitations of currently used shadowgraphs and metal detectors and accurately detect typical charges of various types of explosives concealed in carry-on baggage and on individuals, and which may operate as a stand alone system or work in concert with existing systems; a system for enhancement of shadowgraphs by adequate computer-aided detection especially in image processing and interpretation, to provide the viewer with proper cues, and to strengthen the security measures for casual and premeditated threats without significant changes in existing systems and without the need for modification of procedures or additional training of attendants of security terminals; a means to replace or minimize manual search of suspicious articles and carry-on baggage by a means of identification and a means of localization of threats; and a reliable system for detection of concealed explosives and explosive-filled ordnance carded by individuals at security check points, especially in airports, public and government buildings, and critical installations.
Additionally, the magnitude of destruction from detonation of explosives concealed in checked-in baggage and air cargo would be of immeasurable consequence in terms of loss of lives and irreparable economical damage. Nevertheless, concealment of explosives in checked-in baggage and air cargo is believed to have a low likelihood due to exposure of terrorists, if on-board, to risk without having the bargaining power that they may have if the explosives are at hand. In case the threat is flown separately, the only objective would be destruction without the associated publicity of a cause and demands. However, the inadequacy of tracking checked-in baggage and associating each piece of luggage to a passenger on board allows for flying a threat without a risk to the terrorist. Recent events do not dismiss potential problems since explosives can be implanted in checked-in baggage without the associated passenger being on board or a threat can be unwittingly checked-in by an innocent passenger for someone else. Also, isolated suicidal acts and criminal intentions cannot be discounted. Furthermore, the damage of a single incident would have an extensive toll on lives in addition to the psychological, political, and economical impacts.
Existing radiographic imaging approaches and vapor detection systems are not adequate for dense items even with the use of hard x-rays, since dense checked-in baggage and air cargo are the most difficult to interrogate using x-ray transmission systems. Also, the use of nuclear and neutron systems poses problems of potential damage to the content of the baggage or cargo, of lack of public acceptance, of the need for extensive training, and of high implementation costs.
Furthermore, current tracking system used by most airlines allows an opportunity for boarding a checked-in baggage without the associated passenger. Due to the huge number of passengers and baggage being transported via airborne vessels, the task of physically keeping track of individual passengers along with their baggage as they progress through their flight schedule is becoming rather tedious, inadequate and manpower intensive. This is in addition to an increasing potential of breach of security barriers, loss of revenue, and the additional costs incurred in locating misplaced luggage. Recurring events have shown that separation of a passenger from his/her baggage can lead or encourage implantation of explosives and contraband in the often unidentified pieces of luggage which may not be traced to a particular traveler. The inadequacy of checks and the increased rate of omission and commission of errors in the existing tracking system can lead to disruption of the flow of an important portion of the public transportation system and exposure of innocent lives to undue risk.
A computer-aided scheduling and management system has been broadly applied by airline companies, travel agencies, and airports for many years. However, the existing systems are only restricted to static modes of operation; such as information, ticketing, reservation, schedule planning, and flight confirmation. Most of the functions whether done manually or via computers are human intensive and subject to inadvertent or intentional diversion and human errors. of the utmost importance, the present system fails to cope with the dynamically evolving nature of air transport. Keeping track of the dynamics of the movement of airborne passengers and baggage is especially critical with the increasing complexity in situations of heavy air traffic.
Increasing air travel loads with no changes in personnel leads to a high-demand on upgrading concepts of further automation in airport operations. Existing computer facilities; such as "The Official Airline Guide (OAG)" have the capabilities of connecting individual passenger's personal computer to the central information database through a telephone call and a modem. For example, the "Travelshopper" of TransWofid Airlines, and "Easy Sabre" of American Airlines are developed for automated ticket reservation and confirmation. However, all these computer functions provide only the service of static information which cannot ensure or assist in monitoring and verification of the passenger's trip flow. Hence, means for physical tracking of flow of each individual passenger and the accompanying baggage are lacking. Such shortcomings do affect air travel security and anticipated services.
Accordingly, there is a need in the art for a system to track checked-in luggage and a non-vapor, non-nuclear means capable of screening dense baggage and air cargo for detection of typical charges of several pounds of concealed state-of-the-art explosives which may escape existing interrogation capabilities.
Drugs such as cocaine or heroin (as well as designer drugs) are often smuggled in concealed compartments as well as in the open environment aboard marine vessels and aircrafts. The Coast Guard boarding parties are often unable to discriminate between innocent and suspicious compartments during the search of suspected craft in known drug trafficking areas. This is partially due to lack of the necessary and sufficient evidence prior to opening a compartment to avoid unsubstantiated destruction of an area of the vessel or the craft.
Accordingly, there is a need in the art to provide a system for non-destructive remote inspection for use in interdiction of drugs on marine vessels and aircrafts.
Historically, mines and hidden explosive devices have proven to be of significance in both low and high intensity conflicts. Mines destroyed over twenty five percent of the vehicles in World War II. That percentage almost tripled (nearly seventy percent) in Vietnam. The associated loss of personnel makes improvements in countermine technology imperative. Mines come in a wide assortment; including a variety of explosives, whether as primary or secondary charges. Some of the most common explosives are TNT, Amatol, composition B or composition C. Fuzing techniques include pressure, seismic, anti-disturbance, magnetic, trip line or a combination as well as command operated. Casings include metallic or nonmetallic (plastic). Burial depth varies between surface laid and buried. In spite of the vast development in warfare technology, the state-of-the-art for detection of mines and buried explosive devices lag behind. Though, mines have been a major contributor to the increasing lethality of the battle field, current mine detection devices are based on simple but outmoded technologies that lack accuracy in detection. They involve either manual probing or the use of metal detectors. Both methods are manpower intensive, slow and leave human operators exposed to a fire coveting. Misses in detection are not tolerable and false alarms tend to lower the confidence in the whole device and leads to major errors.
Accordingly there is a need in the art for a detection system capable of real time operation at normal troop advance rates, with high detection/false target ratios, and with sufficient standoff to allow foot soldiers or carrying vehicles or aircrafts to avoid engaging a detected mine.
Additionally, a highly dependable detector for mines in combat fields may require the use of two technologies for verification, for elimination of false alarms, and for versatility in application in various situations, such as soil/water coverage, metal/non-metal casings. Accordingly, there is a need in the an for a dual system especially designed for variable combat conditions.
U.S. Pat. No. 4,251,726 (Luis W. Alvarez) relates to deuterium tagging in an amount at least ten (10) times the natural abundance of the deuterium isotope occurrence and to a method of detecting the tagged article, such as explosives concealed in airline luggage includes subjecting tagged compounds with energy quanta sufficient to carry out the reaction D.fwdarw.n+p -2.23 MeV and detecting the number of neutrons generated where n is a neutron, p is a proton and 2.23 MeV is the threshold energy required for the reaction. The apparatus includes a conveyor and a vertically scanning shutter in combination with a linear accelerator for generating the x-ray energy in the order of 4 MeV and a boron triflouride proportional counter for detecting neutrons. Also, U.S. Pat. No. 3,114,832 (Luis W. Alvarez) relates to the use of x-ray technique to detect Barium tagging. Furthermore, U.S. Pat. No. 4,469,623 (Richard D. Danielson and Robert A. Prokop) relates to detection of articles by the use of vapor-permeable microcapsules containing perfuloralkyl bromides as tags for explosives to permit detection of the articles by a gas- electron-capture detector, and U.S. Pat. No. 4,363,965 (Robert K. Soberman, Kenneth Dervitz, Louis L. Pytlewski) relates to a detection/identification method for determining the presence of a Moessbauer isotope-containing taggant in explosives, weapons, currency, tax stamps, identification documents, etc. The detector includes a Moessbauer isotope-containing detecting substance that is identical to the taggant, and a sensing element responsive to the presence of the tagging substance in the carrier material, provided that the Moessbauer isotope of the tagging substance is in a state of resonance excitation and causes excitation of the Moessbauer isotope of the detecting substance.
None of these references teaches the identification of concealed articles without tagging. Tagging explosives or detonator is impractical when dealing with terrorists who have access to variety of explosives produced under uncontrolled conditions and home made explosives.
Great Britain Patent No. 1,566,256 (Anthony Jenkins, Douglas Walter Issrove) relates to a method and apparatus for detecting a constituent in an atmosphere, especially for revealing nitro explosives by detection of emitted vapors. The apparatus comprises two flow paths each containing an electron capture detector and having a common sample inlet, means in one flow path for altering the flow time of the particular constituent, an indicator for receiving a signal path from the detector in that path, and an isolator in the signal path for preventing passage of a signal in the absence of the constituent. This cited reference teaches identification of explosives in case of release of vapor but does not teach detection of hermetically sealed explosives.
Great Britain Patent No. GB 2,057,135 (William Lloyd Rollwitz, James Darwin King, George Andrew Matzkanin) relates to quick screening of suspect letters and packages for the presence of explosives by placing in a holder inside a coil between the poles of a magnet which exerts a constant magnetic field while the coil exerts a pulsed radio-frequency magnetic field orthogonal to the constant magnetic field. U.S. Pat. No. 2,934,966 (James Darwin King, George Andrew Matkanin, William Lloyd Rollwitz) relates to an apparatus and method for detecting explosives by nuclear magnetic resonance materials suspected of containing explosives are exposed to a constant magnetic field and an impulse modulated magnetic high-frequency field perpendicular to the constant field. The methods in both patents do not teach the art of detection of baggage without the potential damage of content and the interference from the presence of metallic objects. The magnetic field can destroy watches and jewelry.
French Patent 2,433,187 (William O. Gregory, Larry H. Capots, Luigi Morelli, John Mulke, III, Thomas A. Nolan, Jr.) relates to electrical circuits for identification of materials in heterogeneous systems, for example explosives in envelopes and parcels using their complex characteristics of dielectric response. The method does not teach the art of detecting various types of explosives, especially those having metallic casing.
Great Britain Patent No. 1,550,887 (Bain Griffith) relates to an apparatus and method for detecting explosives in closed suitcases or packages by irradiating the case with thermal energy neutrons at 0.01-0.1 eV/neutron and measuring the number of neutrons transmitted to determine the amount of nitrogen in the case, irradiating with 106 eV/neutron to convert oxygen to nitrogen-16 which is measured by a Geiger Counter, and comparing the two measurements to determine whether the proportions of nitrogen and oxygen indicate the presence of explosives. A display device is described for a 2-dimensional image useful for scanning luggage to be loaded onto an aircraft.
French Patent No. 2,588,969 (Gerard Grenier) relates to a device for the detection of substances such as explosives and comprises a generator of preferably 14 MeV neutrons for passage through an object suspected of containing an explosive, a Ge detector, and an analysis means coupled to the detector for analysis of the gamma-rays emitted by the object. The nitrogen-oxygen ratio of the object is determined and compared to that for known explosives.
None of these references cited teaches the specific identification of concealed articles by characterization of the chemical and physical composition of explosives using non-vapor and non-nuclear means. Further, none of the references noted hereinabove teaches the use of x-rays for the detection of explosives in baggages.
European Patent No. 0218240 (Luis W. Alvarez) relates to an apparatus and method of detection including using a 40 MeV (or higher energy) x-ray source as a narrow beam emanating from a microiron. Irradiation of nitrogen with high energy x-rays produces 511 keV annihilation radiation from the decay of an exceedingly short-lived isotope of nitrogen reaction 14N (x-rays, gamma, 2 n) 12.sub.N where N is a nitrogen, n is a neutron. The apparatus detects concentrations of nitrogen between 20% and 30% by weight such as is common in explosives. The apparatus uses high resolution imaging to determine nitrogen content in each two inch cube of the bag's volume in two seconds with the ability to re-examine in 16 seconds Nitrogen concentrations and consequently expected concealed explosives are easily mapped in two or three dimensions quantitatively. The method has the disadvantages of false alarms, large size, high cost and the potential escape of exotic nitrogen-free explosives from detection.
U.S. Patent No. 4,817,121 (Hiromu Shimizu; Isao Horiba) relates to an apparatus for checking baggage with x-rays utilizing an x-ray source for irradiating x-rays toward an object to be checked on a conveyor with a fan-shaped beam, an x-ray detector including a plurality of detecting elements aligned along each of two arms of an L-shape arranged so that one arm extends substantially parallel and another arm extends substantially perpendicularly to a conveying surface of the conveyer means with the detecting elements providing electrical signals in proportion to intensity of the detected x-rays passed by and through the object as measured data, and a picture processor for converting the measured data into a picture signal for display on a display device. The picture processor includes a distortion correcting circuit for processing the measured data from the L-shaped x-ray detector so that the measured data corresponds to data obtained by detecting elements arranged along one straight line.
U.S. Pat. No. 4,799,247 (Martin Annis; Paul J. Bjorkholm) relates to an x-ray imaging device for increasing the ability to recognize, in x-ray produced images, materials of low atomic number. A flying spot scanner illuminates an object to be imaged in a raster pattern; the flying spot repeatedly sweeps a line in space, and the object to be imaged is moved so that the illuminating beam intersects the object. At least a pair of x-ray detectors are employed, each pair associated with signal processing apparatus and a display. The two detectors employed (and the associated electrons and display) are selected from a set of three which includes a transmitted detector located at the line in space which is repeatedly traversed by the pencil beam, a forward scatter detector which is located further from the x-ray beam than the object to respond to photons scattered by the object being illuminated out of the path of the beam, and a backscatter detector which is located closer to the x-ray source than the object being imaged and also arranged to detect photons scattered out of the beam path by the object. Also set forth in the above referenced patent, all three detectors and their associated electronics/displays are employed.
U.S. Pat. No. 4,788,704 (Gerhard Donges; Cornelius Koch) relates to an x-ray scanner and detector signal processing system for scanning objects moving on a conveyor path and for processing the detector signals acquired by the scan has a comparator for identifying faulty signals, the comparator being in a control chain for an image storage memory such that, in the event of a faulty detector signal, the contents of a memory row preceding the faulty detector signal are transferred into the memory row into which the faulty detector signal, if a correct signal, would have been stored. The system also includes a correction element for generating a reference signal at 100% radiation intensity in which the mean value of a number of measured signals is formed. The system also includes an element for reducing the amplitude of the useful signal during measurement in comparison to the amplitude allocated to a radiation intensity of 100%.
U.S. Pat. No. 4,783,794 (Rolf Dietrich) relates to a baggage inspection system has a conveyor path disposed between an x-ray source, which generates an x-ray beam, and a radiation detector for detecting radiation passing through articles on the conveyor path. The conveyor path is formed by two surfaces disposed at a fight angle being inclined relative to the horizontal so that articles on the conveyor path are forced by gravity to lie against one of the surfaces. At least one of the surfaces is a moveable surface, and the other surface may also be a moveable surface, or a roller surface or a plate against which the articles slide. The radiation detector may be an angled detector row so as to encompass substantially all of the radiation beam within its field of view. U.S. Pat. No. 4,759,047 (Gerhard Donges; Rolf Dietrich) also relates to a baggage inspection system has a conveying path for moving articles to be inspected through an x-ray beam. The conveyor path is disposed between an x-ray source for generating the beam and a radiation detector. The radiation detector consists of a number of individual detectors, with the number of individual detectors per unit length being greater in a first region of the detector than in a second region thereof. The first region is disposed at the level of the conveying path for optimally displaying the smaller articles transported by the conveyor path, while the second region is suited for display for larger articles.
U.S. Pat. No. 4,599,740 (Arthur P. Cable) relates to a radiographic examination system for performing x-ray examination of large items such as International container units is formed as an installation comprising housings for one or a plurality of x-ray sources such as linear accelerators which in operation transmit a continuous beam of radiation across a conveyor along which the units to be inspected are displaced either continuously or incrementally. The radiation transmitted through a container is detected in a folded sensor screen or array extending on one side and over the position occupied by a container under inspection. The sensor screen or array produces optical signals which are converted into electrical signals by a photo-diode array or a camera system such as a television camera, and transmitted as pulse coded electrical signals by a coding transfer unit to display screens and signal recording equipment where an image of the transmitted information can be displayed and/or recorded for further use.
U.S. Pat. No. 4,539,648 Thomas F. Schatzki) relates to detection of agricultural contraband in baggage using a radiant energy imaging system for selectively enhancing the image of objects having rectangular cross section, such objects being contained in a material having a different density-absorption coefficient product than the objects. In the invention, the gradient image of the spatially resolved transmitted intensity of the radiation is calculated and eroded to preferentially remove the edges of images of objects having rectangular cross section. The invention finds particular use in detecting agricultural contraband contained in baggage or parcels.
U.S. Pat. No. 4,379,348 (David J. Haas; Costas Blionas; Joseph P. Muenzen) relates to x-ray security screening system involving an optical magnification system for viewing magnified portions of articles being inspected in x-ray examination systems. A combination of a full screen lens and at least one magnification lens are provided for variously inspecting the entire article or only suspicious parts thereof.
U.S. Pat. No. 4,357,535 (David J. Haas) relates to an apparatus for inspecting hand-held articles and persons carrying same. The inspection system is provided to simultaneously x-ray inspect hand carried articles and provide metal detection of the person of the carrier. These different inspections are independent, and may be carried out separately from one another. The x-ray inspection involves the insertion of a hand carried item into a chamber, and guiding it along the x-ray inspection station by holding a handle outside of the detector. Metal detection of the person may be accomplished independently by walking through a metal detector arch.
U.S. Pat. No. 4,137,567 (Hans J. Grube) relates to a system for processing passengers and their luggage at civil airports including a passenger processing counter for verifying airline tickets and confirming passenger identity, equipment for conveying large luggage to be separately stowed aboard the plane from the counter to the plane and installations for performing a security check of both the passengers and their hand or cabin luggage. The system is characterized by a movable conveyor belt extending from the passenger passageway for lined-up passengers and the counter in close proximity thereto but inaccessible to the passengers from the station for passenger processing to a point of pickup and handling by secure airport personnel. A passenger security check zone is provided for allowing a security check of the individual passengers and is designed in a manner of a one-way gate for allowing a security check of the individual passengers and is designed in the manner of a one-way gate for allowing only one-way travel of passengers through the passenger passageway from a point immediately following the passenger processing station through to a verification zone which immediately follows the security check zone and where a passenger becomes cleared by the system. A second movable conveyor belt is provided on the opposite side of the passenger passageway and starting immediately prior to the security check zone for the passengers. The second conveyor belt provides a security check of the hand or cabin luggage of the passengers and terminates behind the verification zone. The second conveyor belt is inaccessible to passengers while they are passing through the passenger security check zone and becomes accessible to particular and already cleared passengers so that they may retrieve their security checked hand or cabin luggage after passing through the security check zone and upon reaching the verification zone.
U.S. Pat. No. 3,924,064 (Yasuji Nomura; Koichi Koike; Kazuo Yamamoto) relates to an x-ray inspection apparatus for baggage whereby generating an x-ray image of an object is disclosed. X-rays are radiated to the object in the form of pulses, and the image is converted to a video-signal for one field and recorded. The recorded video-signal is repeatedly regenerated at field cycle until a next video-signal is produced. In such as system, inspection may be made while the object is being rapidly transferred at an extremely low x-ray radiation level. U.S. Pat. No. 3,919,467 (Ridge Instrument Company, Inc.) relates to an x-ray baggage inspection system in which an x-ray generator directs a beam through an object of baggage and the resulting image, appeasing on a fluorescent screen, is scanned by a low light level TV camera and the image stored, the generator being turned on for a selected number of TV scans or frames. The number of frames and thus the intensity of image accumulated and stored in a video scan converter, is controlled by the operator to enable only the radiation exposure necessary to obtain a legible TV image, the image being displayed on a TV monitor.
Westinghouse Research and Development Center (J. R. Schneeberger and W. C. Divens), Pittsburgh, Pa., describes a rapid screening system for airline passenger baggage for explosives using x-ray contrast profiles. The system employs a Ba-133 isotope as the irradiating source and a linear array of scintillation detectors which are sequentially scanned to obtain independent x-ray detection values for each resolution element over the entire bag profile area. Data is digitized and a real-time connectivity analysis is made by an on-board computer to establish the size of each separate object at the same or greater contrast. An alarm is sounded whenever any object exceeds the minimum size associated with the threat object at its detection threshold. Throughput time is such that bags can be screened at the rate of one/second. The system was evaluated through tests at several airports in which nearly 6000 airline passenger bags were screened to obtain their shape/detector profiles.
IRT Corp (Hans J. Weber), San Diego, Calif., disclosed an automated high speed letter bomb detector system as a self-contained unit which combines the high processing throughput rates of modem mail-handling equipment with fully automated mail screening using remote sensing radiometric gaging techniques, real-time data processing, and automated decision implementation. Three nuclear gages are integrated into a multiparameter sensor capable of discriminating between explosives and paper on the basis of a determination of deuterium concentration and of the ratio of high-Z versus low-Z element constituents. The resulting explosives detector determines the presence of explosives in less than 100 ms in letter mail. This rapid detection capability is achieved by optimizing sensor technology and geometry to the case of letter mail. As a consequence, the sensor is specialized for letter mail with a limited application for other uses.
Aerospace Corp (Fredrick L. Roder, Washington, D.C., discloses an explosives detection method using dual-energy computerized tomography wherein the numerical reconstruction of a cross-sectional image of an object from a data set consisting of the line-integral projections of that cross section obtained at different aspect angles is utilized. The adaptation of dual-energy CT to the detection of relatively small mounts (approximately 100 g) of any of a broad spectrum of explosives concealed in suitcases and packages was shown.
The Bechtel CARGOSCANT.TM. system developed in collaboration with American Science and Engineering, Inc. using a Varian Associates, Inc. Linatron disclose a hard transmission x-ray system capable of penetrating a ten (10) inch of steel to detect a hidden pistol.
U.S. Pat. No. 4,139,771 (Manfred Dennhoven; Claus Kunze; Rainhard Kuehn) relates to a luggage inspection apparatus utilizing fluoroscopic examination in conjunction with an x-ray generator, with the fluoroscopic picture being received by a TV camera, the video signals of which are supplied to an intermediate store for ultimate supply to a TV monitor, the camera containing an AC line-coupled pulse generator for synchronizing the camera and the x-ray flash generator, which pulse generator is electrically interconnected with a synchronizing unit which, upon the initiating of a starting pulse, thus likewise synchronously triggers the x-ray flash generator with respect to the AC supply line. Also, U.S. Pat. No. 4,047,035 (Manfred Dennhoven; Claus Kunze, Rainhard Kuehn) relates to a baggage inspection apparatus utilizing an x-ray generator for fluoroscopic examination of luggage and the like in which an x-ray detector is disposed in the beam path of the x-ray generator, operative to control switch means for switching off the high voltage of the x-ray beam generator in the event the intensity and/or duration of the x-ray radiation exceeds a predetermined value.
U.S. Pat. No. 3,678,278 (Le Roy E. Pell) relates to an inspection apparatus for use with an airline ticket and check-in counter includes an x-ray and fluoroscopic examination unit and a frequency modulation monitor, all positioned on a frame adjacent a baggage weighing platform. A sliding x-ray impervious shield is supported on the frame and is positioned over the weighing platform and baggage thereon during the x-ray inspection.
U.S. Pat. No. 4,216,499 (Claus Kunze; Manfred Dennhoven) relates to a baggage inspection system utilizing fluoroscopy of baggage pieces and the like, employing an X-ray flash unit, a television pick-up unit for scanning the x-ray image, storage of the television image and subsequent image reproduction by a television monitor, in which, in accordance with the invention, the memory is a digital solid state memory for the digital storage of a half frame, of an interlaced video frame of the television pick-up unit, with a capacity of 6 to 8 bits per image-point of the image signal to be stored.
However, Science applications international corporation (SAIC), Sunnyvale, Calif. (Richard I. Miller, Gaynor L. Abbott, Sylvia A. Davey, Peter T. Smith) disclose an evaluation of x-ray fluorescence detectors which are presently available for detecting concealed explosives, for example in airplane luggage and cargo. The method is found to be inadequate for concealed explosives, because the areas capable of being detected are too small and the resolution at high count rates is not high enough.
When x-ray fluorescence is used to analyze a sample, the energy of the fluorescent x-rays is proportional to the atomic number of the element. Thus light elements yield very low energy x-rays which cannot penetrate the baggage, and therefore, are not detected. X-ray fluorescence is thus limited to the detection of heavy elements, such as the lead in detonators. In contrast, when x-ray diffraction is used for the analysis, the scattered x-rays have the same energy as the probe beam. Thus, highly penetrating short wavelength x-rays may be used to probe highly absorbing materials. In addition, since each chemical compound has a characteristic pattern, not only are all elements detected, but the actual chemical compounds can be identified. The problem thus becomes one of obtaining an adequate signal to noise ratio.
Nuclear techniques have also been disclosed for mine detection including: U.S. Pat. No. 3,832,545 (John Bartko) which pertains to a nuclear technique for monitoring objects such as luggage and parcels to determine the presence of specified nitrogen containing materials such as explosives as a function of the nitrogen content and concentration profile. Objects to be analyzed to determine the presence of nitrogen are subjected to a thermal neutron environment and the gamma ray radiation produced by the object in response to nitrogen reactions is monitored by gamma ray detectors. The gamma ray detectors produce indications of the nitrogen content of the object and the concentration profile of the nitrogen in the object. The information provided by the gamma ray detectors is processed to determine if the measured nitrogen content and concentration corresponds to a class of nitrogen containing material of interest, i.e. explosives. U.S. Pat. No. 3,982,125 (Frederick L. Roder) which relates to a method and apparatus for compensating for height variations in certain nuclear gauging applications, particularly nuclear mine detection, are disclosed. A source of monoenergetic photons and a pair of detectors are provided. One of the two detectors includes a K-edge filter, whereas the second detector does not. After processing, the outputs of the two detectors are applied to a suitable readout device. The combination of the filtered detector and unfiltered detector provide a means to compensate for any height variation of the source-detector assembly above the medium under study; thereby permitting any change in the average atomic number of that medium to be discerned.
Also, improvement on existing mine detectors based on electromagnetic techniques is disclosed in U.S. Pat. No. 4,004,212 (Donald E. Wortman) which relates to a mine detector system that utilizes an explosive comparator to increase the sensitivity and selectivity. The system utilizes a generator to transmit a signal simultaneously toward the area to be scanned for mines and towards a sample of the explosive sought. Detectors are positioned within the device to receive the reflected signals from both the area to be scanned and the sample explosive. The outputs from both detectors are fed to preferably a null type comparator for correlation. When the two signals correlate, mine presence is indicated.
None of these prior art references disclose a system that utilizes a combination of low or medium energy x-ray transmission, x-ray diffraction and/or x-ray backscattering system for baggage and cargo, or an ultrasonic system for screening of individuals. Also, none of the literature cited teaches the identification of dynamite (granular, 4 percent), C-4 (Military Specs), water gel/slurry/emulsions NH.sub.4 NO.sub.3 (ammonium nitrate), sheet explosives (PETN), TNT, cocaine, and heroin. Also, none of the prior art teaches the combination of an x-ray backscattering detector and prompt gamma detector to detect antipersonnel, antivehicle or anticraft mines at an appropriate standoff.